In various batteries, a lithium secondary battery has such advantages as light weight, high output, and high energy density and is in heavy usage as a power source for devices, such as the small portable electronic equipment and the portable information terminals to support the current information-driven society. Further, the lithium secondary battery has attracted attention as a power source of electric vehicles and hybrid vehicles and is required to realize a higher energy density, improve the safety, and increase in size.
Since a currently commercially available lithium secondary battery uses an organic liquid electrolyte using a combustible organic solvent as a solvent, a safety device preventing temperature increase in short circuit is required to be mounted, or structures and materials for short circuit prevention are required to be improved. On the other hand, the all-solid lithium secondary battery which uses a solid electrolyte instead of the liquid electrolyte and is fully solidified does not use the combustible organic solvent in the battery. Therefore, the safety device can be simplified, and it is considered that the all-solid lithium secondary battery is excellent in production cost and productivity. As an example of the solid electrolyte, there has been known a sulfide-based solid electrolyte.
An electrode body used in an all-solid secondary battery generally comprises a current collector formed of a metal foil and an electrode layer (cathode layer or anode layer) formed on the current collector and containing an active material (cathode active material or anode active material). The electrode layer may contain other materials such as a solid electrolyte and a conductive auxiliary agent in addition to the active material. As a method for producing an electrode body, there has been known, for example, a method using slurry, which contains an electrode material and a solvent. For example, Patent Document 1 discloses a method for producing an electrode body, in which slurry containing an active material, a sulfide-based solid electrolyte, and a solvent is subjected to film-formation, dried, and the resultant is subjected to pressure molded thereafter. Patent Document 2 discloses a method for producing an electrode body, in which slurry containing an active material, a sulfide-based solid electrolyte, a binding agent, and a solvent is applied to a current collector and the resultant is heated and dried under reduced pressure. Patent Documents 3 to 5 disclose a method for producing an electrode body, in which a powder electrode material containing no solvent is used.